I bought an older 844 about 1 yr ago and the motor was bad so I put in a new motor from radio Shack. Now it runs, but the running is erratic. it slows down a good distance from the power supplied tracks and speeds up 2x as fast when it near them. Is there any way to fix this? jai
In my experience Radio Shack motors are fairly low quality, suitable for science fair projects but not up to model railroad standards. Low quality motors have poor brushes, poor brush supports and springing, poor bearings, high current draw, usually just 3 pole armatures, poor magnets, poor low speed performance, cogging, etc. Go to a model railroad hobby shop and get a better motor. Avoid slot car motors which are usually much higher RPM and also not suited to model railroad loco applications. GQ
On or about 2003-12-05, Trainman illuminated us with:
And just in case the OP doesn't see this problem with other locos, chances are that this loco draws more current than others and so the voltage drop is greater and the slowdown will be more pronounced, given a fixed resistance in the trackwork. I'd agree that more wiring is the best solution, but some improvement might occur with checking the loco for stiffness in the moving parts. Certainly my FEF-3 sometimes seems to have a little too much friction. This will increase the current draw.
Odds are it's your wiring that's the problem, not the motor. Yeah, i know you didn't want to hear that!
Get a meter. Turn your power pack up full (no train on the track, of course) Test the power ON THE RAILS where your drops (wires) connect to the rail (dollars to donuts that's where your engine is fastest...)
Now test it where it's slowest... bet it's AT LEAST 1.5 volts lower, mebbe more. I'd also guess you have only one set of wires connected to the track?
How to fix it? Simple... add more power drops to the rails. Run a fairly heavy gauge wire to the place you want to install the srop, then just a few inches (shouldn't need more than a foot...) of lighter gauge wire to connect it to the rails. The heavy wire (bus wire) can run to several locations for drops. Just be sure you get the polarity right when making connections!
I made the assumption :-) that if JaiJef was able to change a motor in a Rivarossi loco then he probably has several locos with which to compare behaviours. He also had the chance to compare "before and after" behaviour of his Rivarossi loco.
If only the altered Rivarossi loco behaves in this manner then problem #1 is a poor quality motor, problem #2 is voltage drop.
The problem as described is PURELY one of layout wiring voltage drop. Neither the loco nor the power pack can tell where they are relative to one another. So, any such location dependent behavior must be a result of inadequate wiring.
Now, it may well be that the particular loco in question pulls sufficient current to make the voltage drop more noticeable than with other locos. But it's still a voltage drop problem if the troublesome loco runs normally near the power source.